You realize that there Northwest/Delta DC-9's are still flying, as are 737-200, 727's and heck even WWII era DC-3's and DC-6's. Age of the plane doesn't mean much, having proper or improper maintenance is whats really important. I fly a 1965 Cessna 150E every day and it doesn't phase me at all.

The safety is more dependent on the airline you are flying. Some airlines in less-developed/less-controlled countries cut corners in maintenance protocols.

Remember, aircraft are expensive pieces of machinery, that, unlike for example personal road vehicles, receive constant, scheduled, highly-regulated professional maintenance, with each part and detail accounted for and each having its own specific lifespan, after which it will be replaced.

US carriers routinely fly aircraft for 30 years or more. And the US, especially its mainline carriers, has a phenomenal air safety record in recent years. If the 734 is flying with a US carrier (which means US or AS), then you should step on it with total confidence.

I was making a point in another thread that BOTH the 737 and A320 had great safety records, in doing this I mentioned that statistically you are almost ten times safer on an Airbus than a Boeing (16 Hull loses compared to 144) – the response was to say that it’s not a fair comparison, and that it would only be fair to compare 737NGs to the A320 – Quite what this means I don’t know. And, yes I did take into consideration that there is almost a third more 737's delivered and they have been in service twice aslong - but there isnt a third more hull loss accidetns, or even twice as many - there is almost 10 times as many as I stated.

Also, when the topic of older aircraft has been discussed and the usual response of “good maintenance” is posted, which I agree is a very valid point. But an equally valid point is that maintenance doesn’t include re-wiring a frame – there have been many accidents in which old wiring has been either the cause, or significantly contributed to the cause.

So, like I said, good look getting a straight answer.

Edit - Not ment to be an "accurate" comparason either, Many of the accidents will not be type related etc.... I haven't gone into each one in detail. Just an interesting statistic thats all.

Quoting Daysleeper (Reply 5):statistically you are almost ten times safer on an Airbus than a Boeing (16 Hull loses compared to 144)

NASA says that fatal accidents are so rare that there is no meaningful statistical analysis to be done from them. It's like statistically-analyzing differences in odds of winning the lottery: in the big picture the win is so rare that you are essentially as likely to win the lottery if you buy a ticket as you are if you do not.

Quoting wjcandee (Reply 6):statistical analysis to be done from them. It's like statistically-analyzing differences in odds of winning the lottery: in the big picture the win is so rare that you are essentially as likely to win the lottery if you buy a ticket as you are if you do not.

The biggest reason that a comparison of all 737s to all A320s is misleading is that early 737s, being much older, have ended up in service with more cash-strapped operators in places with poor oversight and safety records. That explains most recent hull losses of early 737s.

Another reason is that flying was much less safe, everywhere, when the 737 was introduced. That explains most early 737 hull losses. Accident rates have plummeted since the late '60s for all types.

And yet a smaller reason is that the A320 has more recent technology than 737 Classics, and, especially, 737-200s.

It's valid to compare A320 and 737NG, as the aircraft have roughly similar levels of technology. It's also valid to compare A320 with all 737s (which would include NG, the majority of Classics, and possibly an isolated very late -200 frame or two) produced since the start of A320 production.

But comparing the types is really meaningless, because with first-tier operators in countries with good oversight, both have had first-rate safety records, to the point that any differences between them are statistically meaningless, particularly in recent years. The big difference is the higher number of 737s operating in less safe parts of the world with less safe operators.

Quoting Daysleeper (Reply 5):BOTH the 737 and A320 had great safety records, in doing this I mentioned that statistically you are almost ten times safer on an Airbus than a Boeing

All I am going to say is that it is easy to lie with statistics. You can prove anything you want with numbers if you adjust your parameters.

If you actually think that you are 10 times safer flying an A320 than a 737, then that is ok, but you will have a hard time finding a professional with reliability or safety expertise who agrees with you.

If you have never designed an airplane part before, let the real designers do the work!

I am not into debating about Airbus and Boeing. I guess, the question is, mechanically, how long 737-400 will last on average. You may tell me one 737-300 has been flying for 30 years. But that does not explain why many of them have been discommissioned way before 30 years limit. You may correct me on this, for example, by showing me the statistics that 70% of the 737-300 had been flying after 25 years etc.....

I noticed some airlines stopped their 737 service once it gets to 20 years limit (like British Airways?) That's why I thought airlines may want to stretch the serving time of their airplanes beyond what's been recommended by Boeing, due to the economic problem. Of course, this is purely speculative, not to offend anybody. In fact, another question, is, does the manufacture give any recommendations regarding the number of years, mileage or the cycles for their airplanes?
Also was the maintainence of the airplanes effected by the economical/financial troubles facing airline industry?

Quoting jlivin (Reply 19):But that does not explain why many of them have been discommissioned way before 30 years limit.

Has it occurred to you that economics and the state of the economy can have an effect on these sorts of things? Less demand means just that - ie your ability to fill planes in the past can only be done so if you reduce tickets. But if you do that, there's a chance you might make a loss. So what's the point in operating an extra plane when you can have sufficient capacity without having to operate that one plane? And what's the point in holding onto a plane which you're not going to use for quite some time? There are planes like some 777s which are about 15 years old and they've been scrapped. Others which are much younger too.

Quoting jlivin (Reply 19):I noticed some airlines stopped their 737 service once it gets to 20 years limit (like British Airways?)

Why does this matter? Maybe they switched their fleet over to a new Airbus one for reasons such as efficiency?

That's a fairly common misconception that stems from the fairly common design goal of a 20 year service life. The way that's actually implemented is to model some hypothetical "average" airline route structure, model it for 20 years, count up the flight hours and flight cycles, and then design to that hour/cycle count. It's actually hours and cycles, not calendar time, that primarily determine the life of the aircraft.

Operators that burn through hours, or cycles, or both faster than the average used in the design will eat the life before 20 years are up. Others that burn slower can last far more than 20 years. This is why there aren't any 707's in commercial service in the US anymore, but essentially identical KC-135's flying all over the place.

Not really...whether or not an airframe is economical to operate doesn't have anything to do with the state of the economy (other than fuel prices). Bad economies tend to depress demand, which tends to drive older airplanes out faster, not keep them in the fleet.

Quoting Daysleeper (Reply 5):I was making a point in another thread that BOTH the 737 and A320 had great safety records, in doing this I mentioned that statistically you are almost ten times safer on an Airbus than a Boeing (16 Hull loses compared to 144) – the response was to say that it’s not a fair comparison, and that it would only be fair to compare 737NGs to the A320 – Quite what this means I don’t know.

It means the statistical analysis is only valid if the probability of failure is equal across a particular fleet. The A320 fleet is far more homogeneous than the 737 fleet...the probability of failure is *not* uniform across the 737 fleet, so you can't get meaningful statistical data when you work from the whole fleet.

Quoting Daysleeper (Reply 5):And, yes I did take into consideration that there is almost a third more 737's delivered and they have been in service twice aslong - but there isnt a third more hull loss accidetns, or even twice as many - there is almost 10 times as many as I stated.

Correct, because an extremely disproportionate number of old 737's are operated in countries with poor oversight and sometimes dodgy carriers.

Quoting Daysleeper (Reply 5):But an equally valid point is that maintenance doesn’t include re-wiring a frame – there have been many accidents in which old wiring has been either the cause, or significantly contributed to the cause.

Maintenance does include maintaining the wiring (which could drive you to a rewire if you found the right types of problems). Very very few problems are caused by old wiring that's been properly maintained.

Quoting jlivin (Reply 19):I guess, the question is, mechanically, how long 737-400 will last on average. You may tell me one 737-300 has been flying for 30 years. But that does not explain why many of them have been discommissioned way before 30 years limit.

On average, 20 years. For any individual airframe...anywhere from probably about 14 to over 50.

Quoting jlivin (Reply 19):That's why I thought airlines may want to stretch the serving time of their airplanes beyond what's been recommended by Boeing, due to the economic problem. Of course, this is purely speculative, not to offend anybody. In fact, another question, is, does the manufacture give any recommendations regarding the number of years, mileage or the cycles for their airplanes?

Typically you get rid of your older planes in a downturn. They have no (or cheap) leases to break when you park them, and they are the least efficient, and require some extra maintenance.

Now you may also stop deliveries of new planes, but most airlines don't need the capacity during a downturn.

After the Aloha convertible 737 incident, there was a large effort by both the manufactures and FAA to improve the safety on really old aircraft. There are hard limits set by the FAA, but they can be extended with support of the manufacturer and/or lots of work.

Now in fact those figures are not absolutely static.
Indeed, the estimated service goal (total No. of estimated flight cycles) may be extended with time. This is done by a regular review of engineering reports re: structural repairs in each aircraft type, and if in some conditions, the estimated service goal is extended.

I have read a report a couple of years ago, about the DC9 service life being extended to more than 100K. Can't remember if it was 110K or 120K, but it was a number which really got me to raise my eyebrow and openly say "well done, Douglas engineers!"

.

Quoting jlivin (Reply 19):Also was the maintainence of the airplanes effected by the economical/financial troubles facing airline industry?

Everyone wants to say no - but I would have to think there is a tiny drop. What may go up significantly is time on the ground since spare parts inventories may be cut.

I think the worse case for maintenance is the massive outsourcing, sometimes to the lowest bidder.